My home automation software is janky and bad but it works the way I want it to. It's technically open source but I wouldn't recommend it to anyone. I actually run the same software in my car, mostly to handle music, but it has some car-specific features. A fun bit of tech debt here: I wrote it solely for myself but I'm married now, so figuring out how my wife will interact with it (other than texting me to send it a command) has been an interesting new problem to consider.

My library website is similarly jank on the level that mostly only I should use it, though I have worked on generalizing it a bit.